The present invention relates to a structure of a new composite ferrule used in a connector for connecting optical fibers, a manufacturing method of the ferrule, and a connector for optical fibers using the ferrule.
The inventors examined composite ferrules described in gazettes of Japanese Patent Laid-Open Nos. 61(1986)-57912, 2000-111758, and 2000-147320.
First, the composite ferrule disclosed in Japanese Patent Laid-Open No. 61(1986)-57912 gazette is formed by entirely covering the outside of a hard material with synthetic resin, such as ceramic. Second, the composite ferrule disclosed in Japanese Patent Laid-Open No. 2000-111758 gazette has a constitution in which an approximate entirety of a ferrule base made of synthetic resin is covered with a metallic pipe. Third, in the composite ferrule disclosed in Japanese Patent Laid-Open No. 2000-147320 gazette, as shown in FIG. 1, a ferrule base 10 made of ceramic (zirconia) is provided at an end thereof with a flange portion 11 made of metal or synthetic resin.
A ferrule base of a connecter for optical fibers requires high dimensional accuracy in a small-diameter hole for seating an optical fiber, an outer diameter of a cylindrical portion, and the like. Therefore, the ferrule is constituted in the following manner. The ferrule base uses ceramic as a molding material, for example zirconia, and is produced by use of an extrusion molding method or an injection molding method. Furthermore, in order to improve the dimensional accuracy of the ferrule base, the outer circumferential surface of the molded ferrule base and an optical fiber insert hole are subjected to grinding. Subsequently, a flange portion made of metal, for example stainless, is attached to the end of the ferrule base.
Therefore, there has been a problem that a lot of time and labor are required to manufacture the abovementioned ferrule, the amount of production per time unit is thus limited, and a manufacturing cost thereof is hence increased.
The object of the present invention is to solve the abovementioned problem, and particularly to provide a composite ferrule produced at a low cost, in which only a tip portion of a ferrule base is constituted of a hard material such as ceramic or the other hard material, and in which the other portion of the ferrule base and a flange portion are integrally molded with synthetic resin, as opposed to a conventional ferrule base, which has been constituted of ceramic over the whole length thereof. The object of the present invention is also to provide a method of manufacturing the ferrule and a connector for optical fibers using the same.
In order to achieve the foregoing objects, a first aspect of the present invention is a composite ferrule of a connector for optical fibers including a ferrule base and a flange portion. The ferrule base includes: a cylindrical front member made of a hard material having an optical fiber insert hole at the center thereof, and a rear member made by molding synthetic resin with a substantially same diameter as the front member. The rear member has a coated-optical fiber guide hole at the center thereof and is joined to an end of the front member. The flange portion is formed on an end of the ferrule base made of synthetic resin having a coated-optical fiber guide hole.
A small-diameter portion is further preferably formed on an end of the front member, and the rear member is joined to the front member so as to cover an outer circumferential surface of the small-diameter portion with a part of the rear member. Alternatively, the rear member is joined to the front member by a part thereof being molded in a cavity hole provided on an inner circumferential surface of the end of the front member.
Furthermore, a second aspect of the present invention is a method of manufacturing a composite ferrule of a connector for optical fibers, which includes a ferrule base and a flange portion, the ferrule base having a front member and a rear member. The method includes the steps of: fixing the front member in a state where a small-diameter portion of the front member is exposed, and the other portion of the front member is made airtight; airtightly sectioning a cavity portion for forming the rear member and the flange portion by surrounding the small-diameter portion, while airtightly engaging a tip of an insert pin with an inlet of an optical fiber insert hole provided in the front member; and integrally molding the rear member and the flange portion by injecting molten resin to fill the cavity portion.
In addition, a third aspect of the present invention is a method of manufacturing a composite ferrule of a connector for optical fibers, which includes a ferrule base and a flange portion, the ferrule base having a front member and a rear member. The method includes the steps of: airtightly fixing the outer circumferential surface of the front member; airtightly sectioning a cavity portion for forming the rear member and the flange portion, the cavity portion communicating with the rear end of the front member, while airtightly engaging a tip of an insert pin with an inlet of an optical fiber insert hole of the front member; and integrally molding the rear member and the flange portion by injecting molten resin to fill the cavity portion, while integrally molding a part of the tip portion of the rear member on the inner circumferential surface of a cavity hole of the front member.